The presence of a phagocyte-like NAD(P)H oxidase in pancreatic ␤-cells was investigated. Three NAD(P)H oxidase components were found in pancreatic islets by RT-PCR: gp91 PHOX , p22 PHOX , and p47 PHOX . The components p67PHOX and p47 PHOX were also demonstrated by Western blotting. Through immunohistochemistry, p47PHOX was mainly found in the central area of the islet, confirming the expression of this component by insulin-producing cells. Activation of NAD(P)H oxidase complex in the ␤-cells was also examined by immunohistochemistry. The pancreatic islets presented slower kinetics of superoxide production than HIT-T15 cells, neutrophils, and macrophages, but they reached 66% that of the neutrophil nitroblue tetrazolium (NBT) reduction after 2 h of incubation. Glucose (5.6 mmol/l) increased NBT reduction by 75% when compared with control. The involvement of protein kinase C (PKC) in the stimulatory effect of glucose was confirmed by incubation of islets with phorbol myristate acetate (a PKC activator) and bysindoylmaleimide (GF109203X) (a PKC-specific inhibitor). Diphenylene iodonium [an NAD(P)H oxidase inhibitor] abolished the increase of NBT reduction induced by glucose, confirming the NAD(P)H oxidase activity in pancreatic islets. Because reactive oxygen species are involved in intracellular signaling, the phagocyte-like NAD(P)H oxidase activation by glucose may play an important role for ␤-cell functioning.

Exercise is known to improve cognitive functions and to induce neuroprotection. In this study we used a short-term, moderate intensity treadmill exercise protocol to investigate the effects of exercise on usual markers of hippocampal synaptic and structural plasticity, such as synapsin I (SYN), synaptophysin (SYP), neurofilaments (NF), microtubule-associated protein 2 (MAP2), glutamate receptor subunits GluR1 and GluR2/3, brain-derived neurotrophic factor (BDNF) and glial fibrillary acidic protein (GFAP). Immunohistochemistry, Western blotting and real-time PCR were used. We also evaluated the number of cells positive for the proliferation marker 5-bromo-2-deoxyuridine (BrdU), the neurogenesis marker doublecortin (DCX) and the plasma corticosterone levels. Adult male Wistar rats were adapted to a treadmill and divided into 4 groups: sedentary (SED), 3-day exercise (EX3), 7-day exercise (EX7) and 15-day exercise (EX15). The protein changes detected were increased levels of NF68 and MAP2 at EX3, of SYN at EX7 and of GFAP at EX15, accompanied by a decreased level of GluR1 at EX3. Immunohistochemical findings revealed a similar pattern of changes. The real-time PCR analysis disclosed only an increase of MAP2 mRNA at EX7. We also observed an increased number of BrdU-positive cells and DCX-positive cells in the subgranular zone of the dentate gyrus at all time points and increased corticosterone levels at EX3 and EX7. These results reveal a positive effect of short-term, moderate treadmill exercise on hippocampal plasticity. This effect was in general independent of transcriptional processes and of BDNF upregulation, and occurred even in the presence of increased corticosterone levels.

The bradykinin-potentiating peptides from Bothrops jararaca venom are the most potent natural inhibitors of the angiotensin-converting enzyme. The biochemical and biological features of these peptides were crucial to demonstrate the pivotal role of the angiotensin-converting enzyme in blood pressure regulation. In the present study, seven bradykininpotentiating peptides were identified within the C-type natriuretic peptide precursor cloned from snake brain. The bradykinin-potentiating peptides deduced from the B. jararaca brain precursor are strong in vitro inhibitors of the angiotensin-converting enzyme (nanomolar range), and also potentiate the bradykinin effects in ex vivo and in vivo experiments. Two of these peptides are novel bradykininpotentiating peptides, one of which displays high specificity toward the N-domain active site of the somatic angiotensin-converting enzyme. In situ hybridization studies revealed the presence of the bradykinin-potentiating peptides precursor mRNAs in distinct regions of the B. jararaca brain, such as the ventromedial hypothalamus, the paraventricular nuclei, the paraventricular organ, and the subcommissural organ. The biochemical and pharmacological properties of the brain bradykinin-potentiating peptides, their presence within the neuroendocrine regulator C-type natriuretic peptide precursor, and their expression in regions of the snake brain correlated to neuroendocrine functions, strongly suggest that these peptides belong to a novel class of endogenous vasoactive peptides.

It has been shown that ouabain (OUA) can activate the Na,K-ATPase complex and mediate intracellular signaling in the central nervous system (CNS). Inflammatory stimulus increases glutamatergic transmission, especially at N-methyl-D-aspartate (NMDA) receptors, which are usually coupled to the activation of nitric oxide synthase (NOS). Nuclear factor-κB (NF-κB) activation modulates the expression of genes involved in development, plasticity, and inflammation. The present work investigated the effects of OUA on NF-κB binding activity in rat hippocampus and the influence of this OUA-Na,K-ATPase signaling cascade in NMDA-mediated NF-κB activation. The findings presented here are the first report indicating that intrahippocampal administration of OUA, in a concentration that did not alter Na,K-ATPase or NOS activity, induced an activation of NF-κB, leading to increases in brain-derived neurotrophic factor (Bdnf), inducible NOS (iNos), tumor necrosis factor-α (Tnf-α), and B-cell leukemia/lymphoma 2 (Bcl2) mRNA levels. This response was not linked to any significant signs of neurodegeneration as showed via Fluoro-Jade B and Nissl stain. Intrahippocampal administration of NMDA induced NF-κB activation and increased NOS and α(2/3) -Na,K-ATPase activities. NMDA treatment further increased OUA-induced NF-κB activation, which was partially blocked by MK-801, an antagonist of NMDA receptor. These results suggest that OUA-induced NF-κB activation is at least in part dependent on Na,K-ATPase modulatory action of NMDA receptor in hippocampus. The interaction of these signaling pathways could be associated with biological mechanisms that may underlie the basal homeostatic state linked to the inflammatory signaling cascade in the brain.

Streptozotocin has been widely used to mimic some aspects of Alzheimer's disease (AD). However, especially in mice, several characteristics involved in the streptozotocin (STZ)-induced AD pathology are not well known. The main purpose of this study was to evaluate temporally the expression of AD-related proteins, such as amyloid-β (Aβ), choline acetyltransferase (ChAT), synapsin, axonal neurofilaments, and phosphorylated Tau in the hippocampus following intracerebroventricular (icv) administration of STZ in adult mice. We also analyzed the impact of STZ on short- and long-term memory by novel object recognition test. Male mice were injected with STZ or citrate buffer, and AD-related proteins were evaluated by immunoblotting assays in the hippocampus at 7, 14, or 21 days after injection. No differences between the groups were found at 7 days. The majority of AD markers evaluated were found altered at 14 days, i.e., the STZ group showed increased amyloid-β protein and neurofilament expression, increased phosphorylation of Tau protein, and decreased synapsin expression levels compared to controls. Except for synapsin, all of these neurochemical changes were transient and did not last up to 21 days of STZ injection. Moreover, both short-term and long-term memory deficits were demonstrated after STZ treatment at 14 and 21 days after STZ treatment.